#1 key n. metal device shaped in such a way that when it is inserted into the appropriate lock the lock's mechanism can be rotated. wn
#2 key s. [cardinal, central, fundamental, primal] serving as an essential component; "a cardinal rule"; "the central cause of the problem"; "an example that was fundamental to the argument"; "computers are fundamental to modern industrial structure". wn
#3 key n. something crucial for explaining; "the key to development is economic integration". wn
#4 key n. pitch of the voice; "he spoke in a low key". wn
#5 key v. [identify, discover, key out, distinguish, describe, name] identify as in botany or biology, for example. wn
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